This invention relates to a process for preparing dialkylnaphthalene, and more particularly to a method for preparing 2,6-dimethylnaphthalene by alkylation of napthalene and/or 2-methylnaphthalene with, for example, methanol using a zeolite catalyst.
The compound 2,6-dimethylnaphthalene (2,6-DMN) is a high valued commodity chemical which, as a precursor to 2,6-naphthalene-dicarboxylic acid, finds use in the manufacture of polyester resins.
Alkylation of naphthalene or 2-methylnaphthalene (2- MN) with methanol or dimethyl either using a zeolite catalyst is known in the art. ZSM-5 is presently a preferred catalyst for this process.
U.S. Pat. No. 4,795,847 (Weitkamp et al.) describes a process for the preparation of 2,6-dialkylnaphthalenes by selectively alkylating naphthalene or 2-alkylnaphthalene with an alkylating agent such as methanol in the presence of a zeolite catalyst. Specifically disclosed is ZSM-5 as the catalyst.
U.S. Pat. No. 3,775,496 (S. L. Thompson) describes a multistep process for converting 5-m-tolyl-pentene-2 to 2,6- dimethylnaphthalene. The 5-m-tolyl-pentene-2 is first converted to a mixture of dimethyltetralins, which are then dehydrogenated to form alkylnaphthalenes. These are then isomerized to form the 2,6-isomer and the 2,7-isomer.
UK Patent GB 2,133,032 describes a method for preparing dimethylnaphthalene by reacting monomethylnaphthalene with methanol over an alumina, silica, or silica-alumina catalyst.
German Patent DE 3,334,084 mentions the alkylation of naphthalene or alkylnaphthalene with methanol.